The changes in water levels in the High Plains aquifer from the nonirrigation season 1986-87 through the nonirrigation season 1987-88 and from the nonirrigation season 1979-80 through the nonirrigation season 1987-88 are presented in maps for the entire High Plains aquifer area. Water level changes are caused by interacting changes in precipitation, land use, and annual pumpage. Water levels declined from conditions prior to development until 1980 through parts of the High Plains of Nebraska, Colorado, New Mexico, Oklahoma, and Texas. From 1980 through 1987 water level changes were mixed, with declines of more than 10 ft in the highly developed areas of Kansas, New Mexico, Oklahoma, and Texas and relatively stable to rising water tables throughout the remaining aquifer area. The net change was a rise of 0.8 ft. The 1981-87 period was generally wetter than normal and pumping for irrigated agriculture was therefore reduced. Water level changes were mixed during 1987. Declines continued in some highly developed areas, but water levels generally rose throughout most of the aquifer. The average area-weighted change was a rise of 0.28 ft. This rise was due to the generally greater than normal precipitation, decreased acreage under irrigation, and decreased pumpage for those areas irrigated. At the end of the growing season, the drought in the Midwest in 1988 affected only limited areas of the High Plains. The effects of the drought on water levels can not be assessed until the water-level measurements for the nonirrigation season of 1988-89 are compiled.
